Re: [PATCH] mkdumprd: reduce lvm2 memory under kdump

[Dave Young]

On 03/29/17 at 03:26pm, Xunlei Pang wrote:
> On 03/29/2017 at 03:10 PM, Dave Young wrote:
> > Hi Xunlei,
> >
> > On 03/29/17 at 02:38pm, Xunlei Pang wrote:
> > > We replace "reserved_memory= 8192" with "reserved_memory = 1024"
> > > in /etc/lvm/lvm.conf used by "lvm2", this can save 7MB peak memory
> > > consumption, so we lower the possibility of kdump OOM.
> > >
> > > For kdump, we don't have too many lvm targets, lvm2 locates in the
> > > RAM(rootfs), so don't need that much memory, as discussed with lvm
> > > people, they agree that we can use 1MB under kdump as long as there
> > > are not so many lvm targets invloved.
> > >
> > > We modify /etc/lvm/lvm.conf when "99kdumpbase" install() is executed,
> > > because it is parsed after "90lvm" by dracut.
> > > Signed-off-by: Xunlei Pang
> > >
> > > dracut-module-setup.sh | 5 +++++
> > >  1 file changed, 5 insertions(+)
> > >
> > > diff --git a/dracut-module-setup.sh b/dracut-module-setup.sh
> > > index 1f96bb8..674f3ee 100755
> > > --- a/dracut-module-setup.sh
> > > +++ b/dracut-module-setup.sh
> > > @@ -743,4 +743,9 @@ install() {
> > >      # target. Ideally all this should be pushed into dracut iscsi module
> > >      # at some point of time.
> > >      kdump_check_iscsi_targets
> > > # For the lvm type target under kdump, in /etc/lvm/lvm.conf we can safely replace
> > > # "reserved_memory = 8192" with "reserved_memory = 1024" to lower memory pressure
> >
> > The code is setting reserved_memory = 1024 unconditionally, not only for
> > relacing 8192 with 1024, need update the commit to match the code. Also
> > the line is too long as well.
>
> It only does replacing actually, but if lvm.conf doesn't exist, the code actually does nothing.

Yes, I got that, what I means is if someone set it as
reserved_memory=4096 we still set it to 1024, so the comment just say
8192 -> 1024. We can just say we will unconditionally set it as 1024.
> > > sed -i -e 's/(^[[:space:]]*)reserved_memory[[:space:]]*=[[:space:]]*[[:digit:]]*/ \
> > >              \1reserved_memory = 1024/' ${initdir}/etc/lvm/lvm.conf &>/dev/null
> >
> > Nitpick, this can be changed to 80 columns alignment, like move sed -i
> > -e in a seperate line.
>
> ok, but it's a little hard for shell, we have many code very long including dracut, what about the following, I make each independent part one line?
>     sed -i -e \
>         's/(^[[:space:]]*)reserved_memory[[:space:]]*=[[:space:]]*[[:digit:]]*/\1reserved_memory = 1024/' \
>         ${initdir}/etc/lvm/lvm.conf &>/dev/null

Yes, it is better, maybe less indent for the last two lines, it will be
within 80 columns
> Regards,
> Xunlei
> > > }
> > >
> > > 1.8.3.1
> > > _______________________________________________
> > > kexec mailing list -- [e-mail]
> > > To unsubscribe send an email to [e-mail]
> >
> > Thanks
> > Dave
>
> kexec mailing list -- [e-mail]
> To unsubscribe send an email to [e-mail]